Browsing by Author "Silva, Larissa L."

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    Bridging population pharmacokinetic and semimechanistic absorption modeling of APX3330
    (Wiley, 2024) Silva, Larissa L.; Stratford, Robert E.; Messmann, Richard; Kelley, Mark R.; Quinney, Sara K.; Medicine, School of Medicine
    APX3330 ((2E)-2-[(4,5-dimethoxy-2-methyl-3,6-dioxo-1,4-cyclohexadien-1-yl)methylene]-undecanoic acid), a selective inhibitor of APE1/Ref-1, has been investigated in treatment of hepatitis, cancer, diabetic retinopathy, and macular edema. APX3330 is administered orally as a quinone but is rapidly converted to the hydroquinone form. This study describes the pharmacokinetics of APX3330 and explores effect of food on absorption. Total plasma quinone concentrations of APX3330 were obtained following oral administration from studies in healthy Japanese male subjects (single dose-escalation; multiple-dose; food-effect) and patients with cancer patients. Nonlinear mixed effects modeling was performed using Monolix to estimate pharmacokinetic parameters and assess covariate effects. To further evaluate the effect of food on absorption, a semi-physiologic pharmacokinetic model was developed in Gastroplus to delineate effects of food on dissolution and absorption. A two-compartment, first order absorption model with lag time best described plasma concentration-time profiles from 49 healthy Japanese males. Weight was positively correlated with apparent clearance (CL/F) and volume. Administration with food led to an 80% higher lag time. CL/F was 41% higher in the cancer population. The semi-physiologic model indicates a switch from dissolution-rate control of absorption in the fasted-state to gastric emptying rate determining absorption rate in the fed-state. Oral clearance of APX3330 is higher in patients with cancer than healthy Japanese males, possibly due to reduced serum albumin in patients with cancer. Delayed APX3330 absorption with food may be related to higher conversion to the more soluble but less permeable hydroquinone form in the gastrointestinal tract. Future work should address pharmacokinetic differences between APX3330 quinone and hydroquinone forms.
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    Do maternal demographics and prenatal history impact the efficacy of betamethasone therapy for threatened preterm labor?
    (BMC, 2021-06-24) Kinney, Mary T.; Quinney, Sara K.; Trussell, Hayley K.; Silva, Larissa L.; Ibrahim, Sherrine A.; Haas, David M.; Obstetrics and Gynecology, School of Medicine
    Background: Betamethasone (BMZ) is used to accelerate fetal lung maturation in women with threatened preterm birth, but its efficacy is variable and limited by the lack of patient individualization in its dosing and administration. To determine sources of variability and potential opportunities for individualization of therapy, the objective of this study was to evaluate maternal factors associated with development of neonatal respiratory distress syndrome (RDS) in a cohort of women who received betamethasone. Methods: This study prospectively enrolled women, gestational ages 23-34 weeks, who received betamethasone for threatened preterm birth. Maternal demographics, prenatal history, and neonatal outcomes were abstracted from hospital records. RDS was the primary outcome. Associations between RDS diagnosis and maternal demographics, prenatal history, and betamethasone dosing were evaluated in a case-control analysis and multivariable regression adjusted for gestational age at delivery. Secondary analyses limited the cohort to women who delivered within 1 or 2 weeks of betamethasone dosing. Results: Of 209 deliveries, 90 (43 %) resulted in neonatal RDS. Within the overall cohort and controlling for gestational age at birth, RDS was only associated with cesarean births compared to vaginal births (adjusted OR 1.17 [1.06-1.29]). Route of delivery was also the only significant factor related to RDS in the 83 neonates delivered within 7 days of BMZ dosing. However, among 101 deliveries within 14 days of betamethasone dosing and controlling for gestational age at birth, women who experienced preterm premature rupture of membranes (PPROM) had lower RDS rates than those without PPROM (57.9 % vs. 80.2 %, adjusted OR 0.81 [0.67-0.99]). Maternal age, BMI, race, and ethnicity were not associated with RDS in the regression models. Conclusions: Of maternal characteristics analyzed, only delivery by cesarean was associated with neonatal RDS after antenatal betamethasone use.
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    Pharmacokinetics of vaginal versus buccal misoprostol for labor induction at term
    (Wiley, 2022) Vorontsova, Yana; Haas, David M.; Flannery, Kathleen; Masters, Andrea R.; Silva, Larissa L.; Pierson, Rebecca C.; Yeley, Brittany; Hogg, Graham; Guise, David; Heathman, Michael; Quinney, Sara K.; Obstetrics and Gynecology, School of Medicine
    The IMPROVE study (NCT02408315) compared the efficacy and safety of vaginal and buccal administration of misoprostol for full-term, uncomplicated labor induction. This report compares the pharmacokinetics of misoprostol between vaginal and buccal routes. Women greater than or equal to 14 years of age undergoing induction of labor greater than or equal to 37 weeks gestation without significant complications were randomized to vaginal or buccal misoprostol 25 μg followed by 50 μg doses every 4 h. Misoprostol acid concentrations were determined using liquid chromatography-tandem mass spectrometry for the first 8 h in a subgroup of participants. A population pharmacokinetic model was developed using NONMEM. Plasma concentrations (n = 469) from 47 women were fit to a one-compartment nonlinear clearance model. The absorption rate constant (ka ) was dependent on both route and dose of administration: buccal 25 μg 0.724 (95% confidence interval, 0.54-0.92) h-1 ; 50 μg 0.531 (0.37-0.63) h-1 ; vaginal 25 μg 0.507 (0. 2-1. 4) h-1 ; and 50 μg 0.246 (0.103-0.453) h-1 . Relative bioavailability for vaginal compared to buccal route was 2.4 (1.63-4.77). There was no effect of body mass index or age on apparent clearance 705 (431-1099) L/h or apparent volume of distribution 632 (343-1008) L. The area under the concentration-time curve to 4 h following the first 25 μg dose of misoprostol was 16.5 (15.4-17.5) pg h/ml for buccal and 34.3 (32.5-36.1) pg h/ml for vaginal administration. The rate of buccal absorption was two times faster than that of vaginal, whereas bioavailability of vaginal administration was 2.4 times higher than that of buccal. Decreased time to delivery observed with vaginal dosing may be due to higher exposure to misoprostol acid compared to buccal.
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    Physiologically based pharmacokinetic modelling in pregnancy: Model reproducibility and external validation
    (Wiley, 2021-08) Silva, Larissa L.; Silvola, Rebecca M.; Haas, David M.; Quinney, Sara K.; Medicine, School of Medicine
    Aims Physiologically based pharmacokinetic (PBPK) models have been previously developed for betamethasone and buprenorphine for pregnant women. The goal of this work was to replicate and reassess these models using data from recently completed studies. Methods Betamethasone and buprenorphine PBPK models were developed in Simcyp V19 based on prior publications using V17 and V15. Ability to replicate models was verified by comparing predictions in V19 to those previously published. Once replication was verified, models were reassessed by comparing predictions to observed data from additional studies in pregnant women. Model performance was based upon visual inspection of concentration vs. time profiles, and comparison of pharmacokinetic parameters. Models were deemed reproducible if parameter estimates were within 10% of previously reported values. External validations were considered acceptable if the predicted area under the concentration–time curve (AUC) and peak plasma concentration fell within 2-fold of the observed. Results The betamethasone model was successfully replicated using Simcyp V19, with ratios of reported (V17) to reproduced (V19) peak plasma concentration of 0.98–1.04 and AUC of 0.95–1.07. The model-predicted AUC ratios ranged from 0.98–1.79 compared to external data. The previously published buprenorphine PBPK model was not reproducible, as we predicted intravenous clearance of 70% that reported previously (both in Simcyp V15). Conclusion While high interstudy variability was observed in the newly available clinical data, the PBPK model sufficiently predicted changes in betamethasone exposure across gestation. Model reproducibility and reassessment with external data are important for the advancement of the discipline. PBPK modelling publications should contain sufficient detail and clarity to enable reproducibility.